The invention concerns a linear guide unit comprising:
a guide housing configured as a profiled girder having a bottom wall and a side wall, said bottom and side walls defining an empty guide space and forming an angle of less than 180xc2x0 with each other in cross-section,
a guide rail fixed on one of the bottom wall and the side wall, said guide rail being partially surrounded by at least one sliding traveler supported thereon, and
a carriage plate fixed on the traveler and projecting out of an open side of the profiled girder, said carriage plate having a connecting surface for connection to a connecting structure that is to be moved in a longitudinal direction of the guide housing.
A linear guide unit of the pre-cited type is known from EP 0 340 751 B1. The empty guide space of this linear guide unit is formed by a profiled girder from whose bottom plate two parallel side walls extend upwards and comprise on their upper ends, the longitudinal opening for a carriage plate designated as a connecting body is arranged. This arrangement therefore renders access to the guide rail and to the traveler, which slides thereon in the closed empty guide space, difficult, and is a drawback during maintenance work.
It is an object of the invention to provide a linear guide unit which is easy to service and in which the guide rail and the traveler can be laid bare in a simple manner for maintenance work.
This and other objects and advantages of the invention will become obvious from the following detailed description.
The invention achieves the above objects by the fact that, for a further delimitation of the empty guide space, a cover sheet is detachably fixed on the side wall in an end region thereof opposing the bottom wall, the longitudinal opening for the carriage plate being arranged between a free end region of the cover sheet and the bottom wall. The use of the cover sheet results in an effective closing of the empty guide space from the exterior. The cover sheet can be easily dismounted at all times so that the interior of the guide housing and the guide rail arranged therein, as also the other parts of the linear bearing, can be inspected and serviced without the entire linear guide unit having to be disassembled.
The bottom wall and the side wall of the profiled girder may form an angle of 90xc2x0 with each other in cross-section. The profiled girder may be an extrusion molded aluminum profile or may be made of steel or plastic. The guide rail may be fixed on the bottom wall or on the side wall.
A toothed rack parallel to the guide rail may be fixed on the guide housing in the empty guide space, with which toothed rack, a toothed pinion comprising a drive shaft meshes, said toothed pinion being rotatably mounted on the traveler assembly formed by the traveler and the carriage plate. The toothed pinion and the drive shaft may be rotatably mounted in a pedestal fixed on the carriage plate.
A flexible traction element guided by a deflector roller that is mounted on each longitudinal end of the guide housing may act on the carriage plate, the deflector roller being rigidly connected to a coaxial driven shaft. The mounting of the deflector roller can be effected in a deflector housing.
The traveler may be mounted on the guide rail either for sliding motion or through rolling elements. The toothed rack may be fixed on the same wall (bottom wall or side wall) as the guide rail, and the guide rail and the toothed rack may also form an assembly. However, it is also possible to fix only the toothed rack on one of the two walls and only the guide rail on the other wall. Thus, the traveler can be moved along the guide rail with the help of the toothed rack and the drive shaft comprising the toothed pinion. For this, a flexible traction element is not required.
The guide rail and/or the toothed rack can be mounted in a groove or in contact with a stop edge of the profiled girder and be secured against lifting-off by suitable fastening means such as screws and/or positive engagement, force-locking or gluing. The toothed rack can be mounted in a similar manner.
It is also possible to fix two travelers on the carriage plate that partially surround the guide rail while being arranged thereon behind each other in longitudinal direction. The two travelers can also be arranged spaced from each other on the carriage plate. By the use of a second traveler, a higher capability of transmission of occurring forces and moments is obtained in the linear guide unit.
Rolling bearings are particularly suitable for mounting the toothed pinion and the drive shaft in the pedestal, but it is also possible to use sliding bearings for this purpose.
The use of a flexible traction element makes it possible to drive a driven shaft synchronously to the linear motion of the carriage plate. The flexible traction element which serves to drive the driven shaft can also form a part of the cover of the guide housing and close the longitudinal opening thereof at a location where the pedestal is not situated. A belt, a toothed belt or a strap, for example, can be used as a flexible traction element. This is firmly connected to the carriage plate of the traveler assembly and guided by a deflector roller in the region of each end of the guide housing.
The guide rail can be fixed with screws on the guide housing configured as a profiled girder. The exact fixing location of the flexible traction element may be adjustable in the longitudinal direction of the guide housing so that the pre-stress acting on the flexible traction element can be adjusted. If the flexible traction element forms a part of the cover and contributes to closing and sealing the longitudinal opening of the guide housing, an escape of lubricant from the guide house is also prevented. The flexible traction element is used as a part of the cover of the guide housing even if no driven shaft is provided in the linear guide unit.
The invention will now be described more closely with reference to the appended drawings.